hFE is a transistor parameter that denotes its gain ratio.

This is also called β So if you see a bipolar transistor hFE, gain, or β, it's the same item referenced with different terms.

In technical terms, hFE for a transistor is the gain ratio of the collector current (output) divided by the base current (input). This gain is measured in a transistor circuit called the Common Emitter with a specific Collector Current and Collector Voltage. For example, if 200mA is produced in the collector circuit by a base current of 2mA, that transistor gain is 100. When transistors are made, production lots will have a spread, or range of hFE. Production testing sorts the hFE by "ranks."

For many ROHM bipolar transistors, the gain rank is denoted by a letter suffix in the part number. (Some bipolar devices do not require this letter suffix such as dual (Complex), JEDEC P/N (e.g. MMST2907A), Darlington and Digital Transistors (DTC/DTA). These bipolar devices do have gain, but hFE is already specified as a certain gain range - and for these, the hFE rank code letter does not apply.)

As an example with a hFE letter suffix, the 2SC2412K transistor part number construction has the taping code after the basic part number, followed by the hFE rank letter. As per the data sheet, Q, R and S are available, which is a hFE of 120 to 270, 180 to 390 and 270 to 560 respectively. So full part number would be 2SC2412KT146Q, 2SC2412KT146R, or 2SC2412KT146S.